Updated docs to reflect what the code really does
This adds a few new methods to Command including:-
* A full constructor that takes descriptio, usageMassage and aliases for convenience
* getLabel() which returns the active label for a command, which is derived from the Command name or subsiquent call to setLabel(..)
* A number of registration functions for use in the CommandMap implementer
Also of note is Command.getAliases() no returns the "active" aliases
By: stevenh <steven.hartland@multiplay.co.uk>